We developed a drop infiltrometer that allows measuring Ke on small plots under simulated rainfall intensities that vary between experiments. Infiltration experiments were conducted on a winter wheat field in the Belgian Loess Belt and various surface and soil properties were measured. Furthermore, photos were taken of the soil surface during the infiltration experiments for the determination of the inundated surface fraction.
The results of the experiments show that Ke is strongly dependent on rainfall intensity. In a statistical approach a dynamic Ke could be estimated with a function of rainfall intensity, tillage treatment, percentage residue cover and bulk density. Observations indicate that microtopography, surface fraction covered by a sedimentary seal and macroporosity interact with rainfall intensity, surface ponding and infiltration.
We propose that Ke in physically based infiltration models should either be made dependent on dynamic state variables in a mechanistic way, such as ponding depth and water content or made dependent on rainfall intensity using an empirical relationship. With such adaptations, both surface runoff and erosion models might have more potential to deal with scale effects in runoff generation.